1. June 26, 2003 GI-Tage 2003 Workshop Workshop: Semantics in GDI Werner Kuhn Institute for Geoinformatics kuhn@ifgi.uni-muenster.de

3. June 26, 2003Semantics in GDI 3 Goals  To work towards a better understanding of semantic problems in a GDI  To exchange information on use cases  To exchange experiences with methods and tools This is not a tutorial on semantic technologies – your contributions and questions are requested throughout the workshop.

4. June 26, 2003Semantics in GDI 4 Overview 1.The problem  Use case  Analysis  Generalization 2.Solution attempts  Puzzle pieces  Putting the pieces together  Puzzling questions

5. June 26, 2003Semantics in GDI 5 The Problem: a use case  Shortest path for oversized vehicle

6. June 26, 2003Semantics in GDI 6 Perspective of a Service Developer  Input: two locations: origin and destination e.g., end of A43 to Schloss in Münster vehicle and load specifications total width, weight, min. radius for turns other constraints time, cost, safety  Output: shortest path satisfying (some of) the constraints driving instructions

7. June 26, 2003Semantics in GDI 7 Searching for information  Road data local government: MS_Strassen state: ATKIS industry: TeleAtlas MultiNet (GDF)  Navigation services wayfinding web services: lack information shortest path services: not available online re-use existing local code (shortest path) service chain with filter on graph

8. June 26, 2003Semantics in GDI 8 What information can the data provide? Ergebnisse der erweiterten Suche: XtraWMS - GDI Testbed I Mapping Service: Straßendaten im Netz Beschreibung: Xtra Web Map Server von interactive instruments bereitgestellt für das GDI Testbed I. Der Server präsentiert das Netz der klassifizierten Straßen basierend auf dem OKSTRA-Standard im Bereich von sechs TK-Blättern im Raum Düsseldorf. WMS (1.1.0) Dienst erstellt: 2001-09-08 18:45:00 Kontakt interactive instruments GmbH, Reinhard Erstling, Geschäftsführer erstling@interactive-instruments.de Trierer Straße 70-72 53115 Bonn NRW, Germany Lage zeigen ShowOperations Online Ressource aufrufen Der Zugang zu diesem Dienst ist nicht kostenpflichtig. erstling@interactive-instruments.de Online Ressource aufrufen

9. June 26, 2003Semantics in GDI 9 From data files and documentation  MS_Strassen polylines, a few attributes  ATKIS ATKIS OK several hundred pages, human-readable, online Teil D3 Verkehr: Objekttyp 3101 Strasse linienförmig GN Geographischer Name BRF Breite der Fahrbahn “…setzt sich zusammen aus den Breiten der Fahrstreifen, der befestigten Rand-/Leitstreifen sowie der Stand- oder Kriechspuren (befestigte Straßenoberfläche)” BRV Breite des Verkehrsweges “…Abstand der seitlichen Begrenzungslinien entsprechend der Objektdefinition in Form der jeweils oberen Grenzen der o.a. Klasseneinteilung”...

10. June 26, 2003Semantics in GDI 10 From data files and documentation (2)  TeleAtlas MultiNet ISO Standard GDF (Geographic Data Files) ca. 700 pages, to purchase from DIN Release Notes MultiNet Germany 34 pages, to purchase with product MultiNet Data Specifications 1249 pages, to purchase with product Roads and Ferries Width (in cm): „The width of a Road Element..., a lane or a Road Furniture or Structure Feature.“ Maximum Width Allowed (in cm): „The maximum width limit of a vehicle that may use the Road Element,... The limit is normally set by a physical obstruction such as a bridge or a legal restriction.“ Both attributes are not implemented in MultiNet

11. June 26, 2003Semantics in GDI 11 What‘s left?  Take road axes from GDF road width (BRF) from ATKIS  Obtain both data sources try to read them in your GIS licensing  Build service architecture  Build navigation service

12. June 26, 2003Semantics in GDI 12 ATKISGDF MulitNet Middleware Servlet Engine Web Feature Server Middleware Servlet Engine Web Feature Server WFS ClientFilter ServiceNavigation Services Navigation Client (Browser) GML Java FeatureCollection HTML OpenGIS Components Architecture for Multi-source Navigation Chain

13. June 26, 2003Semantics in GDI 13 Caveats  „schema integration“, „data integration“  „data interoperability“  Semantics of road width  Semantics of passable  Information Communities vs. natural languages  Feature identity in geographic data  Data quality (completeness, currency,...)

14. June 26, 2003Semantics in GDI 14 A Summary of Semantic Problems  Specify the meaning of the question „passable for oversized transport“: width? turns? weight? noise?  Find data with potentially useful contents ATKIS, ALKIS, GDF, OKSTRA,...  Find services with potentially useful functionality shortest path, filter,...  Determine the meaning of feature classes road, „komplexe Strasse“,...  Determine the meaning of attributes „Breite der Fahrbahn“, „Breite des Verkehrsweges“, „maximum width allowed“  Determine the meaning of service operators shortest path

15. Semantic interoperability problems e.g., building heights from floors e.g., directions from graphs e.g., parcels touching a road data-service service-service service-user

16. June 26, 2003Semantics in GDI 16 Solution Attempts  A vision  Pieces of the puzzle Metadata Catalog services Ontologies Reasoning systems Semantic translators

17. June 26, 2003Semantics in GDI 17 Vision Users of geographic information should be able to refer thematic data to semantic reference systems, just as they refer geometric data to spatial reference systems. Software should support the  referencing process  projections to simpler semantic spaces  semantic translation among different reference systems.

18. June 26, 2003Semantics in GDI 18 Semantic Reference Systems Spatial Reference System [ISO 19112] „system for identifying positions in the real world“ e.g., geodetic reference systems Temporal Reference System [ISO 19108] „basis against which time is measured“ e.g., calendars Semantic Reference System [t.b.d.] basis on which thematic data are interpreted: ‚forest‘, ‚wetland‘‚ ‚road width‘ etc. e.g., ontologies

19. June 26, 2003Semantics in GDI 19 Semantic Reference Systems Methods and tools for referencing GI terms by grounding (e.g. “move”) projecting (e.g. ferries and roads to edges) translating (e.g. cadastre to navigation)

20. June 26, 2003Semantics in GDI 20 What we have today  multiple semantic reference systems explicit (ontologies, FACs) implicit (in data models, programs, procedures)  a proliferation of tools (e.g., XML-based) exposing semantics (“mark-up language du jour”) designing representation before computation (Roman numerals)  unclear theoretical bases ontologies are theories without testable models they often lack a (sound) typing system and/or axioms upper levels are ill-defined  need for theory and tools: explaining the meaning of terms in (geographic) information to integrate (geographic) information from different sources

21. June 26, 2003Semantics in GDI 21 Ontologies: specifications of concepts in a domain CAP landuse codeCAP landuse label 1Urban 1.AUrban; Residential 1.A.0.aUrban; Residential; Single family...

22. [Visser et al.]

23. June 26, 2003Semantics in GDI 23 clc: CORINE Land Cover categories

24. June 26, 2003Semantics in GDI 24 What it takes  Spatial and temporal reference systems have well-known systems of measures and units e.g, lengths, angles, time well-known algebras for these measures e.g., modulo arithmetic for angles tools for projection and transformation e.g., map projections, coordinate transformations  Semantic reference systems need formalizations of the kind that Descartes provided for space using algebraic specifications (equational theories) mappings among the resulting formal systems using category theory (morphisms)

25. June 26, 2003Semantics in GDI 25 An ontology editor: Protégé  entity-relationship modeling based on frame logic  pre- and post-conditions for operators  interface to Java  open source  good usability  unclear theoretical bases classes vs. Instances (vs. Java classes), contents of pre- and post-conditions

26. June 26, 2003Semantics in GDI 26 :THING :SYSTEM-CLASS :CLASS :STANDARD-CLASS :SLOT :STANDARD-SLOT :FACET :STANDARD-FACET :CONSTRAINT :PAL-CONSTRAINT :ANNOTATION :INSTANCE-ANNOTATION :RELATION :DIRECTED-BINARY-RELATION Coordinate AttributeInstanceCollection FeatureAttributeInstanceCollection RoadsAndFerriesInstanceCollection NestedFeature Level_0 Node Edge NestedEdge Level_1 LineFeature PointFeature Junction LineElement FerryConnection RoadElement Level_2 ComplexFeature Road Ferry Intersection

27. June 26, 2003Semantics in GDI 27 Class Level_2 Abstract Class Extends :THING Direct Instances: None Direct Subclasses: 1.ComplexFeatureComplexFeature 2.RoadRoad 3.FerryFerry 4.IntersectionIntersection

28. June 26, 2003Semantics in GDI 28 DAML-S: a proposal for a service description language  Building on OWL (formerly DAML+OIL)  to deliver the semantics missing in WSDL and other syntactic service descriptions (IDL)  service profiles with model-based pre- and post- conditions  based on RDF  Clearly a language for exposing semantics  Unclear: relationship to domain ontologies? kinds of models to be used?

30. June 26, 2003Semantics in GDI 30 Our tool: Haskell  a modern functional language executable strict type system multiple parameter type classes (Hugs dialect) freely available from www.haskell.orgwww.haskell.org translates nicely into Java (interfaces)  in a nutshell algebraic data types: data Car = Car Position type classes: class LocatedAt object location where location :: object -> location instances: instance LocatedAt Car Position where location (Car pos) = pos

31. June 26, 2003Semantics in GDI 31 An Example: Ferries in GDF level 0 level 1

32. June 26, 2003Semantics in GDI 32 Ferry example: objectives 1.apply the idea of semantic reference systems to a simple example 2.build a semantic reference system 3.demonstrate the use of Haskell as an ontology language 4.test the hypothesis of what went wrong 5.relate to cognitive semantics: affordances, image schemata, blending

33. June 26, 2003Semantics in GDI 33 Layers of Semantic Reference ContentsForm application data modeldata types application objectsdata reference frameupper-level ontology symbol grounding(outside the system) semantic referenceapplication ontology

34. June 26, 2003Semantics in GDI 34 Application Data Model: GDF roads Nodes have Names data Node = Node Name Edges connect two Nodes data Edge = Edge Node Node RoadElements follow Edges data RoadElement = RoadElement Edge FerryConnections follow Edges data FerryConnection = FerryConnection Edge

35. June 26, 2003Semantics in GDI 35 Application Data Model: Vehicles Cars have a Node as location data Car = Car Node CarFerries carry multiple Cars and have a Node location data CarFerry = CarFerry [Car] Node

36. June 26, 2003Semantics in GDI 36 Application Objects road network start = Node "start" end = Node "end" theEdge = Edge start end theRoadElement = RoadElement theEdge theFerryConnection = FerryConnection theEdge vehicles theCar = Car start theCarFerry = CarFerry [theCar] start

37. June 26, 2003Semantics in GDI 37 Reference Frame: Basics named objects class Named object name where name :: object -> name named objects are equal if their names are equal instance (Eq name, Named object name) => Eq object where object1 == object2 = (name object1) == (name object2) located objects class LocatedAt object location where location :: object -> location

38. June 26, 2003Semantics in GDI 38 Reference Frame: Image Schemas a simple link schema class Link link object where from, to :: link -> object other :: link -> object -> object other link object | object == from link = to link | object == to link = from link | otherwise = error "not linked" a simple path schema class Path path object where move :: path -> object -> object

39. June 26, 2003Semantics in GDI 39 Reference Frame: Image Schemas (2) a simple surface schema class Surface surface object where putOn :: object -> surface -> surface takeOff:: object -> surface -> surface isOn :: object -> surface -> Bool conveyances for transportation class (Path path conveyance, Surface conveyance object) => Conveyance conveyance path object where transport :: path -> conveyance -> object -> object

40. June 26, 2003Semantics in GDI 40 Symbol Grounding: Assumptions  Haskell language semantics Data types (Strings, Lists,...) Operational semantics  experiential grounding of image schemas

41. June 26, 2003Semantics in GDI 41 Semantic Reference (1) RoadElements are Paths for Cars instance Path RoadElement Car where move (RoadElement edge) (Car node) = Car (other edge node) FerryConnections are Paths for CarFerries instance Path FerryConnection CarFerry where move (FerryConnection edge) (CarFerry cars node) = CarFerry (doToAll (transport (FerryConnection edge) (CarFerry cars node) cars) (other edge node)

42. June 26, 2003Semantics in GDI 42 Semantic Reference (2) CarFerries are Surfaces for Cars instance Surface CarFerry Car where putOn car (CarFerry cars node) = if (location car == node) then CarFerry (addOne car cars) node else error "Car and CarFerry are not co-located"... CarFerries are Conveyances for Cars instance Conveyance CarFerry FerryConnection Car where transport (FerryConnection edge) carFerry (Car node) = Car (other edge node)...

43. June 26, 2003Semantics in GDI 43 Layers of Semantic Reference ContentsForm application data modeldata types application objectsdata reference frameupper-level ontology symbol grounding(outside the system) semantic referenceapplication ontology

44. June 26, 2003Semantics in GDI 44 Ontology Testing (1) the car is at the end of the road element after moving t1 = location (move theRoadElement theCar) == end the ferry is at the end of the ferry connection after moving t2 = location (move theFerryConnection theCarFerry) == end the car is at the end of the ferry connection after being transported by the ferry t3 = location (transport theFerryConnection theCarFerry theCar) == end the car cannot move on the edge or on the ferryConnection type in: move theEdge theCar type in: move theFerryConnection theCar

45. June 26, 2003Semantics in GDI 45 Semantic Projection projection

46. June 26, 2003Semantics in GDI 46 Ontology Testing (2) Erroneous Semantic Translation edges are paths for cars instance Path Edge Car where move edge (Car node) = Car (other edge node) after adding this axiom, move theEdge theCar executes (but the car is not supposed to move on any edge, as it may be a ferry connection)

47. June 26, 2003Semantics in GDI 47 Conclusions on Solution Attempts  Current standards proposals focus on exposing semantics  Lack of theories and tools for semantic modeling  Spatial reference systems motivate semantic reference systems shown example for a simplified navigation domain implemented semantic referencing, projection, and translation from static ontologies to computational reference systems  Upper-level ontology with meaningful abstractions image schemas: processes in space and time actions afforded by objects in the environment  properties are modeled as functions inherited from classes type classes specify wrappers for legacy data transportation is a blending of the path and surface schemas.

48. June 26, 2003Semantics in GDI 48 In progress 1.evolving upper-level ontology for GI organized as a lattice of type classes with multiple inheritance of behavior 2.semantic interoperability applications environmental planning emergency management storm damage assessment transportation models (topographic to navigation) 3.comparisons with and translation to other approaches description logic approaches (e.g., BUSTER) DAML-S and OWL OBJ...

49. June 26, 2003Semantics in GDI 49 For more information...  MUSIL web site (Muenster Semantic Interoperability Lab): http://musil.uni-muenster.de  recent publications (all at MUSIL web site) Implementing Semantic Reference Systems. AGILE 2003 Semantic Reference Systems. Guest Editorial, International Journal of Geographical Information Science (in print). Modeling the Semantics of Geographic Categories through Conceptual Integration. GIScience 2002. LNCS 2478: 108-118. Ontologies in support of activities in geographical space. International Journal of Geographical Information Science 15(7): 613-631.